1. Field of the Invention
The present invention relates to a bubble separation and an apparatus thereof comprising: (a) a coarse e bubble chamber for generation of coarse gas bubbles with diameters much greater than 80 microns (generally greater than 250 microns) for complete mixing and gas stripping, and (b) a fine bubble chamber for subsequently generation of fine gas bubbles with diameters much smaller than 80 microns, in turn, for flotation clarification of suspended and surface active matters in a water stream. The present invention also relates to chemical treatment, biological treatment, electrolysis, and air emission control. Both continuous bubble separation system and batch bubble separation system are developed.
2. Description of the Prior Art
Various adsorptive bubble separation processes including dissolved air flotation, vacuum flotation, dispersed air flotation, electroflotation, biological flotation, etc. have been attempted by environmental engineers for water and waste water treatment, with various degrees of success.
Dissolved air flotation is an innovative adsorptive bubble separation process, in which extremely fine air bubbles (with diameters less than 80 microns) are required for separation of mainly insoluble suspended solids from an original liquid phase into a thickened scum phase on the liquid surface. The ratio of air volume to liquid volume is only about 1 to 3 percent. In operation, the gas , such as air, is initially dissolved into water under high pressure, thereby producing a pressurized water. By reduction of pressure in stages, the supersaturated dissolved gas in the pressurized water is subsequently released into a water stream under one atmospheric pressure for production of extremely fine gas bubbles.
Diffused air flotation, dispersed air flotation, froth flotation, and foam separation are all conventional adsorptive bubble separation processes, in which coarse air bubbles (with a diameter much greater than 250 microns) are generated under nearly atmospheric pressure in a liquid-gas mixing vessel. A swarm of coarse air bubbles amounting to 400 percent of the liquid's volumetric flow creates turbulence in the liquid stream, and also provides a large air-to-liquid interface area that allows soluble surface active substances to be adsorbed on the air bubbles, and be separated from the original liquid phase, thereby forming a foam or froth phase on the liquid surface.
A vacuum flotation clarifier needs an enclosure over the top, and is connected to a vacuum pump. Under vacuum (i.e. negative pressure) condition inside said enclosure, the gases originally in soluble form in a water stream held by said vacuum flotation clarifier now become extremely fine gas bubbles with diameters smaller than 80 microns. At present, vacuum flotation clarification is not practiced by environmental engineers for water purification or groundwater decontamination due to poor designs and high costs of old vacuum floatation installations.
Electroflotation is another innovative adsorptive bubble separation process in which an anode electrode and a cathode electrode are used as a pair for generation of fine gas bubbles (with diameters smaller than 80 microns) in a water stream held by an electroflotation clarifier in the presence of electrolytes (i.e. ionic minerals) in water.
Biological flotation's theory and principles are presented by Lawrence K. Wang in his report "Theory and Applications of Flotation Processes" (U.S. Dept. of Commerce, National Technical Information Service, Springfield, Va., U.S.A.; Report No. PB86-194198/AS; November 1985). Under anaerobic conditions and in the presence of anaerobic and facultative microorganisms and nitrate ions, extremely fine nitrogen and carbon dioxide gas bubbles are produced biologically to facilitate flotation separation of suspended solids from a water stream held by a biological flotation clarifier.
Various dissolved air flotation clarifies and related apparatuses have been developed by Milos Krofta (U.S. Pat. Nos. 3307701; 4022696; 4184967; 4377485; 4626345; and 4931175), Joseph N. Parlette (U.S. Pat. No. 3820659), Jimmie A. Chittenden (U.S. Pat. No. 4216085), Leonard S. Love et al (U.S. Pat. No. 4303517), and Lawrence K. Wang et al (U.S. Pat. Nos. 5049320; 5068031; 5069783; and 5084165).
Several dispersed air flotation, diffused air flotation, froth flotation, gas stripping, and related apparatuses have been developed by Milos Krofta (U.S. Pat. No. 4157952, Donald E. Zipperian (U.S. Pat. No. 4735709), Jan D. Miller et al (U.S. Pat. No. 4838434), and Lawrence K. Wang et al (U.S. Pat. No. 5122165).
A few electroflotation clarifiers and related theory and principles have been developed by Milos Krofta (U.S. Pat. No. 4673494) and Lawrence K. Wang (U.S. Dept. of Commerce, National Technical Information Service, Springfield, Va., U.S.A., Report No. PB86-194198/AS, November 1985).
It has been a standard practice for environmental engineers to construct separate water treatment units to remove dissolved, colloidal, suspended, volatile, and living contaminants. The use of separate water treatment units for removal of various contaminants separately is technically feasible, but often economically unfeasible.
Still, such individual water treatment units are not flexible for operation. An ideal adsorptive bubble separation unit shall be able to be operated under several operational modes (such as dispersed air flotation, dissolved air flotation, electroflotation, and vacuum flotation), using various gases (such as air, oxygen, nitrogen, helium, carbon dioxide, ozone, chlorine, etc.).
Accordingly, it is an object of the present invention to provide an improved adsorptive bubble separation apparatus using various operational modes and various gas bubbles for flotation.
Another object of the present invention is to provide a combined coarse and fine gas bubbles separation process system and apparatus having a number of unique design features and using gas bubbles with various sizes for improving water treatment efficiently and cost savings. Said combined coarse and fine gas bubble separation process system includes the steps of influent water feeding, water flow measuring, coarse gas bubbling, chemical/microorganism feeding, fine gas bubbling, gas collection and purification, floated scum collection and discharge, settle sludge collection and discharge, and effluent water discharge.
A further object of the present invention is to provide a combined dispersed, dissolved, vacuum and electrolytic bubble separation apparatus for eliminating the need of many separate treatment units or devices, such as: (a) separate dispersed air flotation unit; (b) separate dissolved air flotation unit; (c) separate gas stripping unit; (d) separate vacuum flotation unit; (e) separate electroflotation unit; and (f) separate air emission control unit for adsorptive bubble separation of contaminants from water. While the aforementioned conventional treatment units or devices may be eliminated for cost savings, one or more of them may be adopted to the present invention as a standby when desired or when duplicate units are required by the monitoring agencies.
Still another object of the present invention is to provide a combined coarse and fine bubble separation apparatus having a coarse bubble chamber for generation of coarse gas bubbles with diameters much greater than 80 microns (generally greater than 250 microns) in turn, for complete mixing and gas stripping, and having a fine bubble chamber for generation of fine gas bubbles with diameters small than 80 microns, in turn, for flotation clarification of suspended matter in a water stream. The built-in air emission control means within the apparatus is for more efficient environmental protection and cost savings.
The major differences between the present invention and the state-of-the-art process methods are described below.
The state-of-the-art process methods described by Roger T. Becker (U.S. Pat. No. 4,872,997, issued on Oct. 10, 1989), Marian Szatkowski and Wilfred L. Freyberger (U.S. Pat. No. 4,737,272, issued on Apr. 12, 1988) and John H. Hoge and John H. Hubbard (U.S. Pat. No. 4,203,837, issued on May 20, 1980) all relate to the use of visible coarse air bubbles of various sizes for agitating a liquid stream, in turn for removing oil (U.S. Pat. No. 4,872,997), froth (U.S. Pat. No. 4,737,272) and foam (U.S. Pat. No. 4,203,837) from liquid streams. The method of the present invention, however, relates to the use of visible coarse gas bubbles (much greater than 80 microns in diameter; air or non-air gases) for agitating/mixing/stripping a water stream under turbulent environment created by said coarse gas bubbles, and subsequently the use of extremely fine gas bubbles (much smaller than 80 microns in diameter; air or non-air) for quietly floating contaminants under a non-turbulent environment, creating (but not disturbing) a floating scum layer and a subnatant as a clarified effluent water.
Specifically in the system and method invented by Becker (U.S. Pat. No. 4,872,997), a batch of contaminated oil-coolant mixture is first filtered for removing solids, and then agitated by coarse air bubbles generated by a nozzle diffusion means for removing said oil from said mixture. The method of the present invention does not have a filtration step, does use coarse gas (air or non-air gas) generated by a jet gas diffusion means, a diaphragm diffusion means, an induced gas diffusion means, a porous tube diffusion means, a porous plate diffusion means, a nozzle diffusion means, a mechanical diffusion means, or combinations thereof, for agitation in a Coarse bubbling step, but also uses extremely fine gas bubbles (air or non-air; smaller than 80 microns in diameter) generated by a dissolved gas flotation means, an electroflotation means, a vacuum flotation means, or combination thereof, for quiet flotation without agitation in a Fine Bubbling step.
The froth flotation process method invented by Szatkowski et al (U.S. Pat. No. 4,737,272) is for separation of the floatable phase from the non-floatable phase of a slurry of particulate material in a froth flotation machine comprising a tank, an upper outlet port for discharge of the floatable phase, and a mechanism for delivering coarse air bubbles (in an arrange of 100-500 microns in bubble size in accordance with FIGS. 3-4 of Szatkowski's patent) to the slurry in the tank to form a froth for said froth flotation process. Both small size air bubbles and large size air bubbles to be used by Szatkowski's method are classified as visible coarse air bubbles (greater than 80 microns). The Fine Bubbling step of the present invention relates to a dissolved flotation process method, an electroflotation process method, a vacuum flotation process method, or combination thereof, which utilize(s) extremely fine gas bubbles smaller than 80 microns in diameter. Production of froth is not required for flotation in the present invention.
The process invented by Hoge et al (U.S. Pat. No. 4,203,837; FIG. 10; Column 4, lines 14-68) is again for removal of discrete particulates from liquids by foam flotation (or froth flotation) using coarse air bubbles and recycling a foam liquid, instead of by dissolved air flotation using fine air bubbles and not recycling a foam liquid as in the case of the present invention.
A Japanese patent, No. 61-227894, issued to T. Nishida on Oct. 9, 1986 discloses several batch type vessels for aeration, precipitation and discharging of a received contaminated water at specific timing and control so that at least one treating vessel is in a discharging step. Nishida's invention emphasized its advantage that a flow rate adjustment of either a basin or a sludge collecting device is unnecessary. Again only coarse air bubbles are used in Nishida's aeration vessels. The present invention, however, discloses a combined coarse and fine bubble separation system in which fine bubbles with diameters smaller than 80 microns can only be generated by one of modern dissolved gas flotation means invented by Lawrence K. Wang, Lubomyr Kurylko and Mu Hao S. Wang (U.S. Pat. Nos. 5,049,320 and 5,167,806), Milos Krofta (U.S. Pat Nos. 4,022,696, 4,377,485, 4,626,345, and 4,931,175), etc., one of modern electroflotation means invented by Lawrence K. Wang, Lubomyr Kurylko, and Mu Hao S. Wang (this invention), Laurence R. Goodman (U.S. Pat. No. 5,182,014), Eric Paul Austin (U.S. Pat. No. 4,101,409), Ronald C. Mehl (U.S. Pat. No. 3,523,891) etc., or one of vacuum flotation means invented by Lawrence K. Wang, Lubomyr Kurylko and Mu Hao S. wang (this invention), or other commercially available fine bubble generation means.